Maritime competition is increasingly conducted through calibrated coercion below the threshold of armed conflict. Nowhere is this more evident than in the South China Sea.
The South China Sea has become one of the clearest contemporary illustrations of how maritime borders are contested not through open naval warfare but through persistent, calibrated coercion operating below the threshold of armed conflict.
In recent years, confrontations between China and regional claimants, particularly the Philippines and Vietnam, have increasingly involved the systematic use of coast guard vessels, maritime militias, and non-kinetic force such as water cannons, ramming maneuvers, close-quarters shadowing, and even allegedly dazzling crew members with lasers.
These incidents are part of a sustained operational pattern shaping facts on the water. Collectively, these dynamics illustrate the growing importance of persistent coercion, legal contestation, and operational presence in contemporary maritime security.
Grey-Zone Maritime Operations: Coercion Without War
At the operational level, China has demonstrated an increasingly sophisticated application of “grey-zone tactics”, a spectrum of coercive measures calibrated to remain below the threshold of conventional warfare while still generating cumulative strategic effects.
Incidents at Second Thomas Shoal in the South China Sea illustrate this pattern, where Chinese Coast Guard vessels have employed water cannons, blocking manoeuvres, and controlled collisions to disrupt Philippine resupply missions and impose operational friction. More recent confrontations include incidents around Sandy Cay, involving the use of lasers to temporarily blind crew members, aggressive maneuvering, obstruction of scientific missions
This approach reflects the logic of incrementalism. Analysts frequently describe this as “salami slicing”, a method through which small, individually non-escalatory actions accumulate into meaningful shifts in control over contested spaces.
Coast Guards and Hybrid Maritime Actors
Coast guards have increasingly become frontline instruments of sovereignty enforcement because they provide governments with a lower-escalation mechanism for coercion under the guise of civilian law enforcement. This institutional shift increasingly blurs the distinction between civilian governance and military strategy, creating an environment in which sovereignty is enforced not through decisive battle but through persistent operational presence, legal ambiguity, and administrative pressure.
A defining feature of this operational environment is the increasing reliance on hybrid maritime actors. China’s deployment of coast guard forces and maritime militia - often composed of ostensibly civilian fishing vessels operating under state direction - introduces plausible deniability while maintaining coercive pressure. These actors occupy a legal and operational grey space that complicates attribution, escalation, and response.
For the Philippines, this has translated into repeated confrontations characterized by “harassment, ramming,swarming, and blocking,” as documented across multiple diplomatic protests and operational reports. Vietnam has similarly reported coercive interference, including attacks on fishing vessels and aggressive enforcement patrols within its exclusive economic zone.
The strategic consequence is deterrence asymmetry: conventional naval superiority becomes less decisive when coercion is exercised through actors operating below the threshold of armed conflict. This exposes a limitation of maritime doctrines primarily designed for high-intensity conflict rather than persistent grey-zone competition.
Comparative Dynamics: Asymmetry and Adaptive Responses
In response to China’s superior maritime capabilities, both the Philippines and Vietnam have adopted asymmetrical maritime strategies designed to offset material disadvantages without engaging in direct naval confrontation.
The Philippines has pursued a strategy of operational persistence combined with transparency. Manila effectively transforms tactical incidents into strategic narratives that mobilise international legal and political support. This approach raises reputational costs and international scrutiny without escalating militarily.
By contrast, Vietnam’s approach centres on long-term endurance, maritime persistence, diplomatic hedging, and selective military modernisation. Its incremental capacity-building and selective assertion of sovereignty reflect a longer-term hedging strategy that balances deterrence with risk management.
Both states increasingly rely on external balancing mechanisms, including security partnerships with the United States and Japan, embedding their responses within a broader geopolitical framework.
Lawfare and the Contestation of Legitimacy
Legal contestation remains a central pillar of the South China Sea dispute. China’s “nine-dash line” claim has been rejected by the Permanent Court of Arbitration, which ruled in 2016 that Beijing’s claims lack legal basis under international law. Despite this, China continues to assert control through a constant Chinese Coast Guard and maritime militia presence backed by several man-made islands it created in the South China Sea that are equipped with military facilities.
For the Philippines and Vietnam, the United Nations Convention on the Law of the Sea provides a legal foundation to challenge these claims and frame incidents as violations of a rules-based maritime order. However, the gap between legal legitimacy and enforcement capacity remains significant. While legal rulings shape international narratives, they do not directly alter operational realities at sea.
This tension highlights a broader structural dynamic in international security: the coexistence of formal legal order with informal power-based enforcement.
Policy Implications
Although the analysis centers on East Asia, the implications extend beyond the region. Similar patterns of grey-zone competition are increasingly relevant for other strategically important maritime corridors.
First, this conflict demonstrates that maritime security must be conceptualized as a multi-domain challenge, integrating naval forces, coast guards, surveillance systems, and legal instruments to address hybrid threats.
Second, the centrality of Sea Lines Of Communication (SLOCs) mirrors the region’s strategic dependence on secure maritime trade routes. Although this article focuses on the South China Sea, similar vulnerabilities exist in other strategically significant maritime regions. The Strait of Hormuz, for example, demonstrates how the protection of critical SLOCs also depends upon resilience against grey-zone disruptions, including vessel interference and infrastructure vulnerability.
Third, the South China Sea highlights the importance of combining operational presence with legal positioning and strategic communication. For middle powers, the ability to shape narratives, leverage international law, and build strategic partnerships can serve as an effective counterweight to larger actors.
Taken together, developments in the South China Sea provide one of the clearest contemporary illustrations of grey-zone maritime competition, highlighting how hybrid actors, legal contestation, and persistent coercion increasingly complement conventional approaches to maritime security.
As similar dynamics emerge in other strategically important maritime regions, the lessons of the South China Sea extend beyond East Asia, offering valuable insights for safeguarding sovereignty, protecting critical sea lines of communication, and enhancing resilience in an increasingly contested maritime environment.
